The present invention relates to a method and an apparatus for frame phase conversion which makes it possible, in an apparatus which transmits with time-division/multiplex one set of signals constituted by a plurality of signals each having a frame structure, to transmit the one set of signals after matching frame phases between an above-mentioned one set of plurality of signals each having a frame structure.
As an example of above-mentioned apparatus, a conventional apparatus in which a frame aligner described in NTT Research and Development Report Vo. 28, No. 7, 1987, pp. 210-214 is provided in each of above-mentioned one set of plurality of signals each having a frame structure so as to arrange phases among above-mentioned one set of plurality of signals each having a frame structure has been proposed.
In CCITT (The International Telegraph & Telephone Consultative) recommendations G. 707, G. 708 and G. 709, such a method that respective sets of a plurality of signals each having a frame structure are transmitted after time-division/multiplex in units of byte is adopted. This frame includes a designator called a pointer, which indicates a position in one frame of information contained in a signal having a frame structure. Further, the signal having a frame structure is provided a function justification. With this function, it is possible to absorb wander produced by temperature change in a transmission line when a frame is transmitted by means of a justification byte. When a frame in accordance with above-mentioned CCITT recommendations is applied with transmit processing in a transmission equipment, the wander is absorbed by using justification.
In this case, in order to match frame phases among one set of plurality of signals each having a frame structure and to guarantee time slot sequence integrity (hereinafter referred to as TSSI. TSSI is an abbreviation of Time Slot Sequence Integrity.), justification has to be executed simultaneously on one set of plurality of signals each having a frame structure.